Field of the Invention
This disclosure relates to a sheet conveying apparatus conveying a sheet and an image forming apparatus.
Description of the Related Art
In the related art, image forming apparatuses such as copiers, printers, and facsimiles include an image forming portion, and a sheet conveying apparatus configured to convey a sheet to the image forming portion by conveyance rollers. In the image forming apparatus of the related art, there are cases where a sheet is skewed when the sheet is conveyed due to a conveyance roller being deformed, alignment of the conveyance roller being deviated, or the like. Here, in the image forming apparatus, accuracy of an image forming position considerably depends on a position of a sheet relative to the image forming portion, and thus a major image quality factor is to match a position of the sheet with the image forming portion with high accuracy.
Therefore, in the image forming apparatus of the related art, a skew correcting portion is provided in the sheet conveying apparatus, and the skew of the sheet is corrected by the skew correcting portion, whereby an accuracy of the image forming position is improved. Examples of the skew correcting portion include the one provided with a shutter member biased in a direction opposite to a sheet conveying direction by a biasing portion such as a spring, for example, and configured to cause a front end of the sheet to come into contact with the shutter member.
As described in Japanese Patent No. 5318221, a shutter-type skew correcting portion including a plurality of shutter members is proposed. The plurality of shutter members is provided rotatably coaxially with a shaft of a conveyance driven roller and each of the shutter members has a plurality of abutment surfaces on a peripheral surface thereof. In the skew correcting portion of this configuration, when a forefront portion of the front end of the skewed sheet comes into abutment with the abutment surface of one of the plurality of shutter members, the sheet is stopped in a state of being in abutment with the abutment surface by receiving a reaction force from the abutment surface. Subsequently, when the sheet is further conveyed, the sheet is deflected. As a result of deflection of the sheet in this manner, the front end of the sheet comes into abutment with the abutment surfaces of the plurality of shutter members. Accordingly, the skew of the sheet is corrected, and subsequently, the sheet with the corrected skewness enters a nip between the conveyance roller and the conveyance driven roller, and is conveyed to downstream.
Meanwhile, in recent years, there has been a demand for improvement in the productivity, that is, improvement in the number of sheets on which images are formed per unit time in the image forming apparatus. For this reason, a sheet conveyance speed has been increased, or an interval (hereinafter, referred to as an inter-sheet distance) between a rear end of a sheet and a front end of the following sheet, the sheets being continuously conveyed, has been reduced. In association with the increase in sheet conveyance speed and shortening of the inter-sheet distance as described above, the shutter member is required to return back to a skew correction position in a short inter-sheet distance after the preceding sheet has passed through.
For instance, when the skew of a preceding sheet is corrected, the shutter member of the related art rotates by being pressed by the sheet. When the shutter member is rotated by a predetermined distance, the shutter member is moved toward a position where the skew of the sheet conveyed subsequently is corrected by a following abutment surface, by a cam portion or the like. Even though the shutter member is moved in this manner, the following abutment surface is in contact with an upper surface of the conveyed sheet until the rear end of the preceding sheet passes through the following abutment surface.
Therefore, the movement of the following sheet abutment surface to the position for correcting a sheet skew is performed after the rear end of the preceding sheet passes the shutter member. Thus, the inter-sheet distance between the preceding and succeeding sheets is required to be set such that the front end of the succeeding sheet does not reach the shutter member during a period from when the rear end of the preceding sheet passes through the shutter member until when the following abutment surface moves to the position for correcting the skew of the sheet.